1. Field of the Invention
The present invention relates to a display substrate and a method for manufacturing a display substrate. More particularly, the present invention relates to a display substrate and a method for manufacturing a display substrate, capable of enhancing reliability of a manufacturing process.
2. Description of the Related Art
A liquid crystal display (“LCD”) device includes a display substrate, an opposite substrate and a liquid crystal layer that is interposed between the display substrate and the opposite substrate. A plurality of gate lines and a plurality of source lines that intersect the gate lines are formed on the display substrate. In addition, a thin-film transistor (“TFT”) that is electrically connected to one of the gate lines and one of the source lines, and a pixel electrode that is electrically connected to the TFT are formed on the display substrate. The TFT includes a gate electrode, a channel, a source electrode and a drain electrode. The gate electrode is extended from a gate line. The channel is electrically isolated from the gate electrode and overlaps with the gate electrode. The source electrode is formed from the source line and is electrically connected to the channel. The drain electrode is electrically isolated from the source electrode and is electrically connected to the channel.
In order to manufacture a display substrate, a mask is required. In order to reduce manufacturing time and costs, significant effort has gone into reducing the required number of masking processes. For example, a five-mask process is a manufacturing process in which five masks are used in five processes, one for each process a gate metal patterning process, a channel patterning process, a source metal patterning process, a passivation layer patterning process and a pixel electrode patterning process. A four-mask process is a manufacturing process in which a channel patterning process and a source metal patterning process are performed using one mask in the five-mask process. Recently, a three-mask process has been developed, which is a manufacturing process in which a passivation layer patterning process and a pixel electrode patterning process are performed by one mask in the four-mask process.
In the three-mask process, for example, a lift-off method is used. The lift-off method is that in which a strip solution is infiltrated into an undercut region between a passivation layer and a photoresist pattern, and then the photoresist pattern and a transparent electrode layer that is formed on the photoresist pattern are simultaneously removed to pattern a pixel electrode. However, the undercut is difficult to manufacture in mass production facilities, and thus reliability of a pixel electrode patterning process may be decreased. Also, in order to filter out a floating substance, such as a transparent electrode layer that is separated by the lift-off method, a filter exchanging period for the strip solution may unfortunately be reduced.